Alibag is a coastal town in the Konkan region of the state of Maharashtra in India, situated about 30 km south of Mumbai. It has the administrative headquarters of the Raigad district (previously known as Kulaba district).  It is famous for three things: its beautiful beach, the imposing Kulaba fort and the renowned Alibag magnetic observatory. At low tide, one can walk across the beach to the fort, but can get trapped there if high tide sets in. The observatory is just on the beach and its reflection can be seen in the sea waters from the fort side.

The Kulaba fort was the main base of Shivaji’s navy under Kanhoji Angre, built in 1680 for protection against British, Dutch and Portuguese naval threats from the Arabian Sea.

The Alibag Magnetic Observatory, established in 1904, has provided an uninterrupted record of geomagnetic observations for over a century and it has since been serving as one of the primary magnetic observatories that form a global network.

The first magnetic observatory in India was set up at Colaba, Bombay (now Mumbai), in 1840, not exactly on purpose but by chance. The original plan was to set it up at Aden (now Yemen), which was a major port under the British Empire. For some reasons, the Aden site could not be made ready in time and the instruments that had already been shipped were sent to Bombay instead. A meteorological and time determination observatory had been functioning there at Colaba since 1826, and so the instruments were installed at the same place. The Colaba magnetic observatory started regular observations only in 1846.

Arthur Bedford Orlebar, Professor of Astronomy at the Elphinstone College, Bombay, started the Colaba magnetic observatory and in 1842, he was succeeded by Dr George Buist. In 1865, Mr Charles Chambers of the Indo-European Telegraphic Service took over and he was designated as Director of the Colaba observatory in 1868. He continued as the Director until his death in 1896, when Dr Nanabhai Ardeshir Framji Moos assumed charge as the first Indian Director. Dr Moos had an Engineering degree from the Science College, Poona (now Pune), and had obtained a B. Sc. degree with distinction from the University of Edinburgh. The Colaba observatory came under the purview of the India Meteorological Department in 1899, prior to which it had been under the Government of Bombay.

Restrictions had been imposed around Colaba on the use of electricity and large masses of iron so that the magnetic observations were not vitiated. However, the city of Bombay was growing rapidly and in the year 1900, plans were made to replace horse-drawn tramcars by a tram service running on electric power drawn from overhead wires. Apprehending that this would affect the magnetic observations, the India Meteorological Department, which was operating the Colaba magnetic observatory, decided to move it away.

The location chosen as an alternative was Alibag, a coastal town about 30 km south of Bombay, on the basis of several considerations, like proximity to Bombay, topography, nature of the soil, its sparse population, etc. It was then thought that magnetic observations could be carried out there without electric interference at least for a century.

The Alibag magnetic observatory building was built with Porbandar sandstone, and such care was taken that every individual stone was tested for traces of magnetism. The room housing the instruments was designed to have such a good insulation, that the diurnal variation of temperature would remain within just 1 degree Celsius.After the building was ready and a new set of instruments installed in 1904, parallel observations were made for two years at Colaba and Alibag. This ensured that the Alibag observations would be compatible with those made at Colaba earlier. The Colaba and Alibag measurements together, from 1846 till today, constitute one of the longest series of geomagnetic data in the world.

Only after the two-year parallel data for Colaba and Alibag was analysed and compared, and the results found satisfactory, were Bombay trams given permission to run on electric traction from May 1907.

This story has a personal ending. My father, Ratnakar Hari Kelkar, was born at Alibag in 1901, and he spent his childhood years watching the construction of the observatory with awe and wonder. He used to tell me how throughout his schooling, he had to study and read in candlelight and in the dim illumination of kerosene lamps, until he left for Bombay in search of a job. The growing population of Alibag remained deprived of the benefits of electricity until 1954, when the restrictions on the use of electricity at Alibag were relaxed.

– R. R. Kelkar, May 2007

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